Antarctica's lush, warm past confirmed

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New Zealand once had a climate like Queensland, at a time when palm trees swayed in the balmy subtropical rainforests of Antarctica, new research shows.

A global team of scientists, who left from Wellington, analysed Antarctic pollen and spores, opening a window on the ancient climate of the continent about 52 million years ago, which showed humid weather similar to modern coastal Queensland.

Mean summer temperatures ranged between 20 and 27 degrees Celsius and frost-sensitive vegetation abounded, according to the study, which drilled sub-seabed rock samples from off the coast of what is now known as Wilkes Land, due south of Australia.

Even by the poles, scientists found the ‘Greenhouse' Eocene epoch - 55 to 48 million years ago - was very warm, leading to the growth of "highly diverse, near-tropical forests".

The research, published in the science journal Nature this week, confirmed what many scientists suspected - that Antarctica once boasted an enviable summer.

New Zealand's climate would have been similar during the epoch and there may also have been land mammals, like possums, on Antarctica, said Dr Ian Raine, team researcher and a micro-paleontologist at GNS Science in Lower Hutt.

Apart from recurring ice ages, Dr Raine said, Antarctica had been frozen for just a fraction of its history - the latest freeze starting about 35 million years ago.

The study showed winter temperatures on the Wilkes Land coast during the epoch topped 10C, despite three months of polar blackness.

But the continental interior was noticeably cooler, with a climate supporting temperate southern beech rainforests similar to those found in the South Island today.

The finding highlights extreme contrasts between modern and ancient climates.

The "greenhouse" epoch was the warmest time in the past 66 million years and showed temperature gradients from the pole to the equator were less pronounced than they are now, Dr Raine said.

The study sounds a warning for climate change, with scientists forecasting Earth could again heat up in a few hundred years as fossil fuel burning accelerates carbon dioxide (CO 2) to the levels which allowed the lush forests to thrive near the South Pole.

Back then atmospheric CO 2 concentrations were more than twice as high as today. "If the current CO 2 emissions continue unabated due to the burning of fossil fuels, CO 2 concentrations in the atmosphere, as they existed in the distant past, are likely to be achieved within a few hundred years,” lead researcher Professor Jorg Pross said.

“By studying naturally occurring climate warming periods in the geological past, our knowledge of the mechanisms and processes in the climate system increases. This contributes enormously to improving our understanding of current human-induced global warming.”